Tahiti: The First Direct3D 11.1 GPU

One of the many changes coming in Windows 8 next year will be the next iteration of Direct3D, which will be Direct3D 11.1. More so than any other version of Direct3D so far, D3D11.1 is best summed up as a housekeeping release. There will be some new features, but compared to even past point releases such as 10.1 and 9c it’s a small release that’s going to be focusing more on improving the API itself – particularly interoperability with SoC GPUs for Windows 8 – than it will be about introducing new features. This is largely a consequence of the growing length of time for all matters of development hardware and software. By the time Windows 8 ships Direct3D 11 will be 3 years old, but these days that’s shorter than the development period for some AAA games. Direct3D 11/11.1 will continue to be the current Windows 3D API for quite some time to come.

With regards to backward compatibility in D3D11.1, there’s one new feature in particular that requires new hardware to support it: Target Independent Rasterization. As a result AMD’s existing D3D11 GPUs cannot fully support D3D11.1, thereby making Tahiti the first D3D 11.1 GPU to be released. In practice this means that the hardware is once again ahead of the API, even more so than what we saw with G80 + D3D10 or Cypress (5870) + D3D11 since D3D11.1 isn’t due to arrive for roughly another year. For the time being Tahiti’s hardware supports it but AMD won’t enable this functionality until the future – the first driver with D3D11.1 support will be a beta driver for Windows 8, which we expect we’ll see for the Windows 8 beta next year.

So what does D3D11.1 bring to the table? The biggest end user feature is going to be the formalization of Stereo 3D support into the D3D API. Currently S3D is achieved by either partially going around D3D to present a quad buffer to games and applications that directly support S3D, or in the case of driver/middleware enhancement manipulating the rendering process itself to get the desired results. Formalizing S3D won’t remove the need for middleware to enable S3D on games that choose not to implement it, but for games that do choose to directly implement it such as Deus Ex, it will now be possible to do this through Direct3D.

S3D related sales have never been particularly spectacular, and no doubt the fragmentation of the market is partially to blame, so this may be the push in the right direction that the S3D market needs, if the wider consumer base is ready to accept it. At a minimum this should remove the need for any fragmentation/customization when it comes to games that directly support S3D.

With S3D out of the way, the rest of the D3D11.1 feature set isn’t going to be nearly as visible. Interoperability between graphics, video, and compute is going to be greatly improved, allowing video via Media Foundation to be sent through pixel and compute shaders, among other things. Meanwhile target independent rasterization and some new buffer commands should give developers a few more tricks to work with, while double precision (FP64) support will be coming to pixel shaders on hardware that has FP64 support.

Finally, looking at things at a lower level D3D11.1 will be released alongside DXGI 1.2 and WDDM 1.2, the full combination of which will continue Microsoft’s long-term goal of making the GPU more CPU-like. One of Microsoft’s goals has to been to push GPU manufacturers to improve the granularity of GPU preemption, both for performance and reliability purposes. Since XP things have gotten better as Vista introduced GPU Timeout Detection and Recovery (TDR) to reset hung GPUs, and a finer level of granularity has been introduced to allow multiple games/applications to share a GPU without stomping all over each other, but preemption and context switches are still expensive on a GPU compared to a CPU (there are a lot of registers to deal with) which impacts performance and reliability.

To that end preemption is being given a bit more attention, as WDDM 1.2 will be introducing some new API commands to help manage it while encouraging hardware developers to support finer grained preemption. Meanwhile to improve reliability TDR is getting a major addition by being able to do a finer grained reset of the GPU. Currently with Windows 7 a TDR triggers a complete GPU reset, but with Windows 8 and WDDM 1.2 the GPU will be compartmentalized into “engines” that can be individually reset. Only the games/applications using a reset engine will be impacted while everything else is left untouched, and while most games and applications can already gracefully handle a reset, this will further reduce the problems a reset creates by resetting fewer programs.

 

Building Tahiti & the Southern Islands Partially Resident Textures: Not Your Father’s Megatexture
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  • mavere - Thursday, December 22, 2011 - link

    Seriously!

    With the prevalence of practically silent PSUs, efficient tower heatsinks, and large quiet fans, I cannot fathom why the noise floor is 37.9 dB.
    Reply
  • Finally - Thursday, December 22, 2011 - link

    As usual, AT is shooting straight for the brain-dam, I mean, ENTHUSIAST crowd feat. a non-mentioned power supply that should be well around 1000W in order to drive over-priced CPUs as well as quadruple GPU setups.
    If you find that horrendous they will offer you not to read this review, but their upcoming HTPC review where they will employ the same 1000W power supply...
    Reply
  • B3an - Thursday, December 22, 2011 - link

    *face palm*

    1: 1000+ Watt PSU's are normally more quiet if anything as they're better equipped to deal with higher power loads. When a system like this uses nowhere near the PSU's full power the fan often spins at a very low RPM. Some 1000+ PSU's will just shut the fan off completely when a system uses less than 30% of it's power.

    2: It's totally normal for a system to be around 40 dB without including the graphics cards. Two or 3 fans alone normally cause this much noise even if they're large low RPM fans. Then you have noise levels from surroundings which even in a "quiet" room are normally more than 15 dB.

    3: Grow some fucking brain cells kids.
    Reply
  • andymcca - Thursday, December 22, 2011 - link

    1) If you were a quiet computing enthusiast, you would know that the statement
    "1000+ Watt PSU's are normally more quiet if anything"
    is patently false. 1000W PSUs are necessarily less efficient at realistic loads (<600W at full load in single GPU systems). This is a trade-off of optimizing for efficiency at high wattages. There is no free lunch in power electronics. Lower efficiency yields more heat yields more noise, all else being equal. And I assure you that a high end silent/quiet PSU is designed for low air flow and uses components at least as high in quality as their higher wattage (non-silent/non-quiet) competitors. Since the PSU is not decribed (a problem which has been brought up many times in the past concerning AT reviews), who knows?

    2) 40dB is fairly loud if you are aiming for quiet operation. Ambient noise in a quiet room can be roughly 20dB (provided there is not a lot of ambient outdoor noise). 40dB is roughly the amplitude of conversation in a quiet room (non-whispered). A computer that hums as loud as I talk is pretty loud! I'm not sure if you opinion is informed by any empirical experience, but for precise comparison of different sources the floor should be at minimum 20dB below the sources in question.

    3) You have no idea what the parent's age or background is, but your comment #3 certainly implies something about your maturity.
    Reply
  • formulav8 - Tuesday, February 21, 2012 - link

    Seriously grow up. Your a nasty mouth as well. Reply
  • piroroadkill - Thursday, December 22, 2011 - link

    Haha, yeah.

    Still, I guess we have to leave that work to SPCR.
    Reply
  • Kjella - Thursday, December 22, 2011 - link

    High-end graphics cards are even noisier, so who cares? A 250W card won't be quiet no matter what. Using an overclocked Intel Core i7 3960X is obviously so the benchmarks won't be CPU limited, not to make a quiet PC. Reply
  • Ryan Smith - Thursday, December 22, 2011 - link

    Our testing methodology only has us inches from the case (an open case I should add), hence the noise from our H100 closed loop radiator makes itself known. In any case these numbers aren't meant to be absolutes, we only use them on a relative basis. Reply
  • MadMan007 - Thursday, December 22, 2011 - link

    [AES chart] on page 7? Reply
  • MadMan007 - Thursday, December 22, 2011 - link

    More stuff missing on page 9:

    [AF filter test image] [download table]
    Reply

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